fix(workflows/labeler): grant "issues: write" permission (#25142)

The pr-size-labeler action currently relies on that permission, because it uses 
the issues API (which requires the issues permission), not the labels API (which 
requires either the issues or the pull requests permission).

.github/workflows/labeler.yml

@@ -4,6 +4,7 @@ on:
 
 permissions:
   contents: read # to determine modified files
+  issues: write # pr-size-labeler uses the issues API until https://github.com/CodelyTV/pr-size-labeler/pull/89 is merged
   pull-requests: write # to add labels to PRs
 
 jobs: